Fluid operated pump control system



March 26, 1963 c. J. COBERLY 3,082,749

FLUID OPERATED PUMP CONTROL SYSTEM Filed Dec. 5, 1960 5 Sheet sSheet l44 1&2

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March 1963 c. J. COBERLY 3,082,

FLUID OPERATED PUMP CONTROL SYSTEM Filed Dec. 5, 1960 v 5 Sheets-Sheet 2CLARE-Mas Cl. 625591. 4,

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FLUID OPERATED PUMP CONTROL SYSTEM Filed Dec. 5. 1960 :5 Sheets-Sheet 5Easy .( 134- 130 138 122 j $470 .16! J24- 5 120 J65 12; 2/4- .10 F195 B///s flrrom/egs. 112E215, 57/5574, RUSSELL KEQM inc, Huntington Park,Caiili, a corporation of California Filed Dec. 5, 1960, 'Ser. No. 73,56513 Claims. or. 121-152;

The present invention relates in general to fluid operated bottom holepumps for oil wells and, more particularly, to an improved controlsystem for the engine valve means of such a pump.

As background, a fluid operated pump of the type to which the inventionrelates includes interconnected engine and pump piston means which arereciprocated by applying fluid pressure forces to the engine pistonmeans in opposite directions alternately, whereupon the pump pistonmeans pumps production fluid from the well to'the surface. The engineand pump piston means are movable in at least one direction by anengine-operating fluid pressure differential of P 'P applied to theengine piston means, P being the supply pressure of an operating fluid,such as relatively clean crude oil, and P being the discharge pressurethereof. In many instances, the engine operating pressure differential PP is utilized to displace the engine and pump piston means in bothdirections, but this is not essential to the invention.

The various pressures applied to the engine piston means to reciprocateit and the pump piston means connected thereto are controlled by anengine valve means which includes an engine valve reoiprocable betweentwo operating positions. In one of its operating positions, the enginevalve causes movement of the engine and pump piston means in onedirection, and, in its other operating position, it causes movementthereof in the opposite direction. The engine valve means may beincorporated in the engine and pump unit, as disclosed in my Patent No.2,311,157, granted February 16, 1943, or it may be incorporated in aseparate engine valve unit spaced from the engine and pump unit, asdisclosed, for example, in my Patent No. 2,949,857, granted August 23,1960.

Conventionally, the engine valve of a fluid operated pump isreciprocated by applying thereto in opposite directions alternately thesame fluid pressure differential P P used to displace the engine andpump piston means. Since P -P may vary widely from one well installationto another, it is impossible under such conditions to design a singleengine valve means which will work in all well installations. Actually,a large number of different engine valve means must be available tosatisfy a wide P P range.

Another problem arises because of the fact that the physical propertiesof the operating fluid vary widely, both because such physicalproperties may be inherently diflerent from one operating fluid toanother, and because the physical properties of a given operating fluidvary widely with different pressure and temperature conditionsencountered in different wells. Viscosity is the property which issubject to the greatest variation from one operating fluid to another,and the viscosity of a given operating fluid varies widely dependingupon the temperature and pressure conditions encountered in differentwell installations. For example, a viscosity range of one to as high asten thousand centistokes may be encountered with different operatingfluids and different well conditions. No single conventional enginevalve means can operate satisfactorily throughout such a wide viscosityrange.

Thus, with the wide ranges of engine-operating fluid pressuredifferentials and operating fluid viscosities encountered, it hasheretofore been necessary to utilize a substantial number of differentengine valve means each Patented Mar. 26, 1953 capable of accommodatingonly a narrow range of conditions.

With the foregoing in mind, a primary object of the present invention isto provide an engine valve means wherein the engine valve is movedbetween its two operating positions by a valve-operating fluid pressuredifferential Ap which is completely independent of P and P and which maybe varied to compensate for viscosity variations. With thisconstruction, a single engine valve means may be utilized for anypressure and viscosity conditions that may be encountered, which is animportant feature of the invention.

More particularly, an important object of the inven tion is to provide avalve-operating fluid pressure differential which is small as comparedto the P P values normally encountered, which is independent of P and Pand which is constant except for any variations that may be required toaccommodate viscosity variations. An important advantage of an enginevalve means utilizing a Ap which is small as compared to the P -P valuesnormally encountered is that such an engine valve means can beincorporated in any installation having a value of P P at least equal tothe necessary Ap.

Another important object of the invention is to provide a valveoperating pressure falling between P and P and differing from either Por P by an amount Ap which is small as compared to the P P valuesnormally dealt with. In other words, an object of the invent-ion is toprovide a valve operating pressure which is equal either to P Ap, or toP +Ap, Where Ap is independent of P or of P and is normally smallcompared to P 1P2.

Still another important object of the invention is to provide an enginevalve means having means for varying Ap as a function of the viscosityof the operating fluid so that a larger Ap is available with a moreviscous operating fluid to compensate for correspondingly largerfriction losses in the control passages and orifices of the engine valvemeans, whereby the effective pressure differential actually applied tothe engine valve remains constant.

Since the valve-operating fluid pressure differential Ap utilized todisplace the engine valve between its operating positions is thusindependent of P and P is small as compared to the P --P values normallyencountered, is no greater than the minimum P P value incountered, andis varied as a function of the operating fluid viscosity, it will beapparent that a single engine valve means of the invention willaccommodate wide ranges of viscosities and P and P values since theeffective pressure differential actually applied to the engine valve isconstant.

Another object of the invention is to utilize a value of Ap permittingthe use of turbulent flow orifices for controlling the valve functionswhich are of practical sizes.

It is another object of the invention to provide an engine valve meansof the foregoing nature having means for sensing the load on the enginepiston means and for throttling the engine valve at any time that theload on the engine piston means is below normal.

The foregoing objects, advantages, features and results of the presentinvention, together with various other objects, advantages, featurersand results thereof which will be evident to those skilled in the fluidoperated pump art in the light of this disclosure, may be achieved withthe exemplary embodiments of the invention described in detailhereinafter and illustrated in the accompanying drawings, in which:

FIGS. 1 and 2 are semidiagrammatic vertical sectional views of a fluidoperated pump which embodies the engine valve means of the invention,various parts being shown in different operating positions in the twofigures; FIG. 3 is a semidiagrammatic view, partially in verticalsection and partially in elevation, which is similar to FIGS. 1 and 2but which illustrates another embodiment of a fluid operated pump of theinvention; and

FIGS. 4 and 5 are fragmentary, semidiagrarnmatic, vertical sectionalviews showing alternative embodiments of parts of the engine valve meansof the invention.

Introduction In the drawings, the fluid operated pump incorporating theengine valve means of the invention is shown as comprising a fluidoperated engine and pump unit and a separate engine valve unit locatedin side-by-side relation, both units being adapted to be circulated intoand out of the well hydraulically. Thus, the construction showncorresponds to that of my aforementioned Patent No. 2,949,857.. However,it will be understood that the fluid operated engine and pump and theengine valve means may also be incorporated in a single unit, as shown,for example, in my aforementioned Patent No. 2,311,157. Also, theinvention may be embodied in a fluid operated pump of the set type, asopposed to a fluid operated pump of the free type having one or morecomponents hydraulically circulatable into and out of the well.Furthermore, while the drawings illustrate a closed system, wherein thespent operating fluid at the discharge pressure P is returned to thesurface independently of the production fluid from the Well, it Will beunderstood that the invention may also be utilized in an open system,wherein the spent operating fluid and the production fluid are mixed.

Pump 0 FIGS. 1 and 2 Turning now to FIGS. 1 and 2 of the drawings, thenumeral designates a bottom hole housing having therein, in side-by-siderelation, a chamber 12 for a fluid operated engine and pump unit 14 anda chamber 16 for a separate engine valve means or unit 18 of theinvention. The engine and pump unit 14 is movable between its operatingposition in the chamber 12 and the surface through a tubing 20 forconveying production fluid from the well to the surface. Similarly, theengine valve unit 18 is movable between an operating position in thechamber 16 and the surface through a supply tubing 22 for deliveringoperating fluid at the supply pressure P to the engine valve unit 18 andultimately to the engine and pump unit 14. Also connected to the bottomhole housing 10 is a return tubing 24 for conveying spent operatingfluid at the pressure P to the surface.

Engine and Pump Unit 14 The engine and pump unit 14 includes a housing26 having a tapered lower end which is in engagement with an annularseat 28 on the bottom hole housing 10 when the unit 14 is in itsoperating position. A passage 30 in the housing 10 interconnects thereturn tubing 24 and the chamber 12 above the annular seat 28 so that,by reversing the flow of operating fiuid through the return tubing 24,as is well known in the art, the engine and pump unit 14 may becirculated upwardly through the production tubing 20 to the surface.

Reciprocable vertically in the housing 26 is a tubular engine and pumpplunger 32 constituting the hereinbetore-mentioned interconnected engineand pump piston means. More particularly, the tubular plunger 32includes a tubular upper rod 34 reciprocable in a bore 36 in the housing26, a tubular engine piston 38 connected to the lower end of the upperrod 34 and reciprocable in an engine cylinder 46 in the housing 26, atubular lower rod 42 connected to the lower end of the engine piston andreciprocable in a bore 44 in the housing 26, and a tubular pump piston46 connected to the lower end of the lower rod 42 and reciprocable in apump cylinder 43 in the housing 26. As will be explained hereinafter,the plunger 32 is reciprocated by applying P -P to the engine piston 38in opposite directions alternately, this being accomplished by theengine valve unit 18 under the control of upper and lower annularcontrol grooves 50 and 52 in the upper rod 34. The tubular plunger 32carries a working valve 54 which prevents downward fiow through an axialpassage 56 in the plunger. The lower end of the housing 26 of the engineand pump unit 14 is provided with an inlet 58 in communication with aninlet 60 in the bottom hole housing 10 when the unit 14 is in itsoperating position. Downward flow out of the pump cylinder 48 isprevented by a standing valve 62 in the inlet 58, and drainage of thetubing system when the engine and pump unit 14 is unseated is preventedby a standing valve 64 in the inlet 60. The upper end of the pumpcylinder 48 is connected to the inlet 58 at a point below the standingvalve 62 by ports 66 in the housing 26, an annular clearance 68 betweenthe housings 26 and 10, and ports 70 in the housing 26.

As will be apparent, when P -P is applied to the engine piston 38 in thedownward direction, the plunger 32 moves downwardly and the workingvalve 54 opens while the standing valves 62 and 64 close, this conditionbeing shown in FIG. 1 of the drawings. As shown in FIG. 2, when P P isapplied to the engine piston 38 in the upward direction, the plunger 32moves upwardly and the working valve 54 closes while the standing valves62 and 64 open. Production fluid is displaced upwardly into theproduction tubing 29 during both the upward and downward strokes of theplunger 32. As will readily be recognized by those skilled in the art,the engine and pump unit 14 provides a dilferential double acting pumpin which the differential action is obtained entirely with the pumppiston 46, the engine piston 38 operating as a full double actingengine.

Engine Valve Unit 18 Turning now to the engine valve unit 18 of theinvention, it includes a housing 72 having a tapered lower end whichengages an annular seat 74 on the bottom hole housing 10 when the enginevalve unit is in its operating position. A passage 76 in the bottom holehousing 10 serves to apply fluid pressure to the lower end of the enginevalve unit 18 from the return tubing 24 to circulate the engine valveunit upwardly through the supply tubing 22 to the surface when the flowthrough the return tubing is reversed. As pointed out in myaforementioned Patent No. 2,949,857, the two units 14 and 13 may becirculated out 'of the well simultaneously, or separately.

Vertically reciprocable in the engine valve housing 72 is an enginevalve 78 which includes a differential-area actuator 80, the enginevalve being reciprocable in minor and major bores 82 and 84 in theengine valve housing. The engine valve 78 is a four-way valve capable ofalternately applying P and P to the upper end of the engine piston 38and of simultaneously alternately applying P and P respectively, to thelower end of the engine piston. Thus, the engine-operating fluidpressure differential P P is applied to the engine piston 38 in oppositedirections alternately to reciprocate the plunger 32.

Considering how the foregoing is accomplished, the engine valve 78includes two cylindrical lands 86 and 83 which are disposed in the minorbore 82 and the ends of which have V-shaped throttling grooves thereinto provide for gradual opening and closing of the engine valve, asexplained in my Patent No. 2,311,157. When the engine valve '78 is inits lower operating position, as shown in FIG. 1 of the drawings, theupper land 86 is disposed below a passage connecting the minor bore 82to the upper end of the engine cylinder 40. The upper end of the minorbore 82 communicates with the supply tubing 22 so that, under theseconditions, the supply pressure P is applied to the upper end of theengine piston 38. At the same time, communication between the lower endof the engine cylinder 40 and the return tubing 24 is established by wayof a passage 92, the space between the upper and lower lands 86 and 88of the engine valve 78, and a passage 94. Thus, the discharge pressureP;

in the return tubing 24 is applied to the lower end of the enginepiston, wherefore the engine-operating fluid pressure differential P Pis applied to the plunger 32 in the downward direction.

Turning to FIG. 2 of the drawings, when the engine valve 78 is in itsupper operating position, the discharge pressure P in the return tubing24 is applied to the upper end of the engine piston 38 through thepassage 92, the space between the upper and lower lands 86 and 88 of theengine valve, and the passage 90. At the same time, the supply pressureP in the supply tubing 22 is applied to the lower end of the enginepiston 38 by way of a passage 96 interconnecting upper and lowerportions of the minor bore 82, a space between the lower land 88 of theengine valve and the actuator 80, and the passage 94. Thus, theengine-operating fluid pressure dilferential P -P is so applied to theengine piston 38 as to move the plunger 32 upwardly.

Thus, when the engine valve 78 is in its lower operating position, thelands 86 and 88 are in such positions that they apply P P to the enginepiston 38 in the downward direction. Conversely, when the engine valve'78 is in its upper position, the lands 86 and 88 are in such positionsthat they apply P P to the engine piston 38 in the upward direction.

Considering now the manner in which the engine valve 78 is displacedfrom one of its operating positions to the other, it will be noted firstof all that the upper end of the engine valve, i.e., the upper end ofthe upper land 86 thereof, is constantly exposed to the supply pressureP in' the supply tubing 22. The actuator 80 includes a piston 98reciprocable in the major bore 84 and having at its upper end an annulararea preferably equal to the area at the upper end of the engine valve78 which is constantly exposed to the supply pressure P The annular areaof the upper end of the piston 98 is constantly exposed to a valveoperating pressure of P Ap which is produced in a manner to be describedhereinafter. As hereinbefore outlined, Ap is small as compared to the PP values normally encountered and is independent of P and P Thus, theengine valve 78 is constantly biased downwardly by the supply pressure Pand the valve operating pressure P Ap applied to equal areas of theengine valve, the supply pressure P acting on the upper end of theengine valve and the valve operating pressure P Ap acting on the upperend of the piston 98. In order to produce movement of the engine valve78 upwardly into its upper position, the supply pressure P is applied tothe lower end of the piston 98, the lower end of this piston having anarea preferably equal to twice the annular area of the upper endthereof. Conversely, in order to move the engine valve 78 downwardlyinto its lower position, the valve operating pressure P Ap is applied tothe lower end of the piston 98. It will be apparent that, with the arearelationships outlined, the upward and downward forces applied to theengine valve 78 in moving it to its upper and lower positions are equalsimply to Ap, minus friction losses.

Considering how P and P Ap are alternately applied to the lower end ofthe piston 98, when the engine and pump plunger 32 reaches the upper endof its travel, as shown in FIG. 1 of the drawings, the lower controlgroove 52 in the upper rod 34 bridges two control passages 108 and 182leading to the upper rod bore '36. The control passage 100 communicateswith the major bore 84 adjacent the lower end thereof through an orifice104 of the sharp-edge type. The control passage 102 communicates withthe upper end of the major bore 84, where, as will be described, thevalve operating pressure of P Ap is constantly available. Under theseconditions, the valve operating pressure of P -Ap, less friction losses,is ap' plied to the lower end of piston 98, whereupon the engine valve78 moves downwardly into its lower position to initiate downwardmovement of the engine and pump 6' plunger 32 under the influence of theengine-operating fluid pressure diiferential P -P On the other hand,when the engine and pump plunger 32 reaches the lower end of its travel,as shown in FIG. 2, the upper control groove 50 in the upper rod 34bridges two control passages 106 and 108 leading to the upper rod bore36. The control passage 106 communicates with the upper end of the minorbore 82 and thus contains the operating fluid at the supply pressure PThe control passage 108 leads to an intermediate portion of the majorbore 84 and, when the engine valve 78 is in its lower position,communicates with the lower end of the piston 98 through a wide externalannular channel in the piston 98, through another orifice 104, identicalto the orifice 104 mentioned previously, and formed in the piston 98,and through an axial passage 112 in the engine valve actuator 80. Underthese conditions, the supply pressure P less friction losses, is appliedto the lower end of the piston 98 to initiate upward movement of theengine valve 78 toward its upper position preparatory to applying theengine-operating fluid pressure difierential P P to the engine and pumpplunger 32 in the upward direction.

In addition to the control orifices 104, one formed in the'engine valvehousing 72 and the other in the actuator piston '98, the actuator 80 isprovided therein with two vertically spaced control orifices 114 and twovertically spaced control orifices 116, all of the sharp-edge type andall communicating with the axial passage 112 in the actuator. When theengine valve 7 8 is in its lower position, the orifices 114 and 116 arepositioned as shown in FIG. 1 relative to the major and minor bores 82and 84. When the engine valve 78 is in its upper position, theseorifices are positioned as shown in FIG. 2 relative to the minor bore 82and an annular clearance 118 which is spaced upwardly from the upper endof the major bore 84.

The purpose of the control orifices 104, 114 and 116 is to cause theengine valve 78 to move from each of its operating positions to theother at three successively different speeds. The first speeds of theengine valve 78 in its two directions of movement are controlled by theorifices 104, the second speeds by the orifices 114, and the thirdspeeds by the orifices 114 and 116 in parallel. Such three-speedengine-valve movement is explained in detail in my aforementioned PatentNo. 2,311,157, the disclosure of which is incorporated by reference sothat a complete explanation herein is unnecessary.

The foregoing describes the manner in which the engine valve 78 isshifted in both directions by the valve-operating fluid pressuredifferential .Ap, less friction losses, as the result of alternatelyapplying the supply pressure P and the valve operating pressure P Ap tothe lower end of the actuator piston 98. The manner in which the valveoperating pressure P Ap is produced will now be considered.

Valve Operating Pressure Control The engine valve housing 72 provides acylinder, having major and minor bores 120 and 122, for a control valve124 which includes a plunger having major and minor pistons 126 and 128respectively disposed in the major and minor bores 120 and 122. Thevalve 124 controls flow of the operating fluid from the upper portion ofthe minor bore 122, which upper portion, as will become apparent, actsas a source 130 of operating fluid at the valve operating pressure P.Ap, to the return tubing 24 by way of a passage 132. The source 130* ofP -.Ap communicates with the upper end of the major bore 84 for theactuator piston 98 through a passage 134, thereby supplying operatingfluid at the valve operating pressure to the upper end of the major bore84.

Considering the forces acting on the control valve 124, it is biasedtoward its closed position, wherein it prevents flow from the source 130to P by Way of the passage 132, by the operating fiuid at the supplypressure P applied to the lower end of the major piston 126 through apassage 136 connected to the passage 96. The valve 124 is biased towardits open position, wherein it permits the discharge of pressure from thesource 130 to P by the pressure P Ap acting on the upper end of theminor piston 128 and by a spring 138.

Considering the action of the control valve 124 as thus far described,it will be apparent that the spring 138 determines the magnitude of thevalve-operating fluid pressure differential Ap. In other words, thespring 138 maintains the valve 124 in such a position as to maintain thepressure in the source 130 substantially constant at P Ap, the spring,in effect, subtracting the pressure increment Ap from P If the pressurein the source 130 tends to rise above P Ap, the valve 124 moves toward amore open position to dissipate the excess pressure to P by way of thepassage 132. On the other hand, if the pressure in the source 130 tendsto fall below the value P Ap, the valve 124 moves toward a more closedposition to permit the pressure in the source 130 to build up to P Apagain. In this connection, it should be pointed out that there is aconstant leakage flow of operating fluid from the annular clearance 118around the valve actuator 80 into the upper end of the major bore 84 forthe actuator piston 98, the annular clearance 118 always containingoperating fluid at the supply pressure P as the result of the presenceof the passage 96. This leakage flow from the annular clearance 118 intothe upper end of the actuator piston bore 84 takes place through thenormal working clearance between the actuator 80 and the portion of theminor bore 82 lying between the annular clearance 118 and the major bore84. This leakage path is symbolized in FIGS. 1 and 2 of the drawings bya restricted passage 140 which, of course, does not actually exist.Since the actuator piston bore 84 is connected to the source 130 by thepassage 134, the symbolic leakage passage 140 provides a means ofreplenishing any pressure loss in the source 130 below P1"Ap.

The spring 138 is selected to provide the desired Ap for application tothe engine valve 78. For example, it has been found that selecting aspring 138 which will produce a Ap of from 500 to 1,000 p.s.i. givesexcellent results. Thus, assuming a spring 138 which will provide a Apof 1,000 psi, and assuming that the pumping conditions are such as tomake P and P 10,000 p.s.i, and 5,000 p.s.i., respectively, it will beseen that the engine valve 78 is operated by alternately applying to thelower end of the actuator piston 98 the supply pressure P of 10,000p.s.i. and a valve operating pressure P Ap equal to 9,000 p.s.i. Undersuch conditions, which are more or less typical, the engine valve 78 isoperated by a Ap which is quite small as compared to theengine-operating fluid pressure differential of F -P the latter being5,000 p.s.i. under the conditions specified. Furthermore, Ap iscompletely independent of P and P For example, in an installation whereP is 5,000 p.s.i. and P is 2,500 p.s.i., Ap will still be 1,000 p.s.i.under the conditions outlined. Thus, with the present invention, thesame engine valve 78 may be used throughout a wide range of P and Pvalues since the effective pressure differential actually applied to theengine valve remains constant.

In general, the desired .Ap can be obtained as long as P P is at leastequal torthe desired value. In relatively shallow wells, where columnpressures are relatively low, Ap may approach P P In deeper wells,however, Ap becomes relatively small as compared to P P Generallyspeaking, Ap will always be at least slightly less than P P Thus, theaddition of the pressure control valve 124 to the engine valve 78 in theenvironment set forth insures that the engine valve can be utilizedthroughout a wide range of pressures with no change in its performancesince it is always operated by the same effective pressure differential.Thus, it is not necessary to supply different engine. valves 78 fordifferent pressure conditions, which is an important feature of theinvention.

Alternative Valve Operating Pressure Control Instead of operating theengine valve 78 by applying thereto the supply pressure P, and a valveoperating pressure lower than P by an amount Ap, the engine valve can beoperated by applying thereto the discharge pressure P and a valveoperating pressure higher than P by an amount Ap. In other words,instead of subtracting a relatively small amount from P to obtain avalve operating pressure, a valve operating pressure can be obtained byadding a relatively small amount to P The structure for accomplishingthis is shown in FIG. 5 of the drawings.

Referring thereto, the numeral 142 designates an engine valve housinghaving therein a cylinder 144 for a control valve 146 which includes apiston 148. The upper end of the cylinder 144 constitutes a source 150of a valve opera-ting pressure of P +Ap. The valve 146 controls flow ofthe operating fluid into the source 150 from a passage 152 whichcommunicates with a source, not shown, of the operating fluid at thesupply pressure P Considering the forces acting on the valve 146, it isbiased downwardly toward its closed position by the valve operatingpressure P -l-Ap acting on the upper end of the piston 148. The valve146 is biased upwardly toward its open position by the dischargepressure P acting on the lower end of the piston 148 through a passage154, and by a spring 156 which is selected to give the desired value ofAp. As will be apparent, if P +Ap becomes too high, the valve 146 movestoward its closed position. On the other hand, if P -j-Ap becomes toolow, the valve 146 moves toward its open position. The net result isthat the pressure in the source 150 is maintained substantially constantat P +Ap.

The valve operating pressure in the source 150 is applied to an enginevalve, not shown, similar to the engine valve 78 through a passage 158.It will be understood that, in this instance, the engine valve is movedbetween its operating positions by applying P and P +Ap to equal andopposite areas in an alternating manner, just as P, and P Ap are appliedto equal and opposite areas of the engine valve 78 in an alternatingmanner.

Viscosity Compensation In general, the present invention provides meansfor increasing the valve-operating fluid pressure differential Ap, abovethe Ap value produced by the spring 138, as a function of the viscosityof the operating fluid in order to compensate for the increased pressuredrops through the various control passages and control orificesassociated with the engine valve actuator 80. In other words, the objectis to progressively increase Ap at the source 130 sufliciently as theviscosity of the operating fluid increases that the efiective fluidpressure differential actually applied to the engine valve 78 remainsconstant, thereby offsetting the increasing pressure drops in thevarious control passages and control orifices resulting from anincreasing operating fluid viscosity.

To accomplish the foregoing, the invention adds to the force applied tothe pressure control valve 124 by the spring 138 a fluid pressure forcewhich increases as a function of the operating fluid viscosity toprovide a Ap which similarly increases with increasing viscosity. Theamount that the fluid pressure force added to the spring force increaseswith an increased operating fluid viscosity is so selected as to makethe effective fluid pressure differential actually applied to the enginevalve 78 the same at the increased viscosity as it was at the lowerviscosity.

More particularly, it will be noted that the passage 136, which containsoperating fluid at the supply pressure P is connected to the upper endof the major bore 120 through an orifice 160 of the sharp-edge,turbulent flow type, the flow through such an orifice beingsubstantially independent of viscosity. The point of connection to theupper end of the major bore 120 lies between the orifice 160 and acapillary restriction 162 which connects the orifice 160, and the upperend of the major bore 120, to the passage 132 containing the operatingfluid at the discharge pressure P As is well known, the flow through thecapillary restriction 162 is directly proportional to the absoluteviscosity of the operating fluid.

With the foregoing construction, a compensating pressure, acting in adirection to open the control valve 124, is applied to the annular areaat the upper end of the major piston 126. This compensating pressure hasthe desired effect of increasing Ap at the source 130 with an increasein the operating fluid viscosity, with the result that a reduction inthe actual fluid pressure differential applied to the engine valve 78with increasing viscosity is avoided. By selecting proper sizes for thesharp edged orifice 160 and the capillary restriction 162, thecompensating pressure applied to the annular area at the upper end ofthe major piston 126 may be varied as a function of viscosity in such amanner as to maintain constant the fluid pressured differential actuallyacting on the engine valve 78. In other words, increasing pressurelosses in the control passages and control orifices associated with theengine valve 78, as the operating fluid viscosity increases, are offset.Thus, the same engine valve unit 18 may be used irrespective of theviscosity of the operating fluid, which is an important feature of theinvention.

Considering an illustrative example of the magnitude of the viscositycompensating force which must be added to the force produced by thespring 138, it is typical in an engine valve unit like the unit 18 forthe various control passages associated with the engine valve 78 to havea pressure drop therethrough, at an operating fluid viscosity of onecentistoke, of only approximately of the total pressure drop through thecontrol passage and the control orifices 104, 114 and 116, the controlorifices accounting for 90% of the total pressure drop under suchconditions. Since the control orifices are of the sharpedge type, thepressure drops therethrough do not increase significantly withincreasing operating fluid viscosity, the effect of viscosity on such anorifice being negligible from Reynolds numbers of 1,000 to infinity.However, increasing viscosity increases the pressure drops through thecontrol passages approximately as the 0.2 power of the viscosity.

From the foregoing, it can be shown that the ratio of the total pressuredrop, through the control passages and control orifices, at a viscosityof 10,000 centistokes,

to the total pressure drop at a viscosity of one centistoke, isapproximately 1.53: 1. Consequently, the fluid pressure differentialactually applied to the engine valve 78 can be maintained constant underthe foregoing conditions throughout a viscosity range of one centistoketo 10,000 centistokes by so selecting the sizes of the orifice 160 andthe restriction 162, and the annular area of the upper end of themajor-piston 126, that the compensating force added to the forceproduced by the spring 138 is 53% of the spring force at a viscosity of10,000 centistokes.

It will be understood, of course, that the foregoing example is merelyintended as illustrative and that various factors, such as the relativeflow resistances of the control passages and control orifices, determinethe magnitude of the compensating force which must be added to thespring force -to achieve the Ap necessary to provide a constanteffective fluid pressure differential at the engine valve 78 atdifferent viscosiites.

- Alternative Viscosity Compensator Instead of locating the orifice 160and the restriction 162 externally of the control valve 124 as shown inFIGS.

1 and 2 of the drawings, an orifice 164, corresponding thusinterconnecting the lower end of this piston and the annular area at theupper end thereof. The capillary restriction 166 is formed by a portionof the working clearance between the minor piston 128 and the wall ofthe minor bore 122, this portion of the working clearance beingconnected to the P passage 132 by an annular groove 168 and a passage170.

It will be understood that the hereinbefore-discussed viscositycompensation principle may also be applied to the construction of FIG. 5wherein the valve operating pressure is P +Ap, instead of P -Ap. Again,the object would be to increase Ap at the source as a function of theoperating fluid viscosity.

Governing The present invention adds to the pressure control and theviscosity compensation for the engine valve 78 a governing means,similar to that of my aforementioned Patent No. 2,311,157, for limitingthe speed of the engine and pump plunger 32 whenever the load thereonfalls below a predetermined value, as may occur when free gas is presentin the pump cylinder 48, when the pumping rate exceeds the productivecapacity of the well, and the like. This governing means is designatedgenerally in FIGS. 1 and 2 of the drawings by the reference numeral 172.

The governing means 172 includes a differential-area pilot valve 174having major and minor portions 176 and 178 respectively reciprocable inmajor and minor bores 180 and 182. The upper end of the minor portion178 has an area of one constantly exposed to the discharge pressure Pthrough a passage 184, and the upper end of the major portion 176 has anannular area of one constantly exposed to the supply pressure P througha passage 186 communicating with the passages 136 and 96. The lower endof the major portion 176 of the pilot valve 174 has an area of twoalternately exposed to the supply pressure P and the discharge pressureP through a passage 188 connected to the passage 94. Thus, when theengine valve 78 is in its lower position, as shown in FIG. 1, thedischarge pressure P is applied to the lower end of the pilot valve 174so that this valve occupies its lowermost position. Conversely, when theengine valve 78 is in its upper position, as shown in FIG. 2 of thedrawings, the supply pressure P is applied to the lower end of the pilotvalve 174 so that it assumes its upper position.

When the pilot valve 174 is in its lower position, as shown in FIG. 1,an external annular channel 190 in the minor portion 178 thereof bridgespassages 192 and 194, the former being connected to the control passage1102' and the latter being connected to the lower end of the major bore84 for the actuator piston 98 of the engine valve 78. However, when thepilot valve 174 is in its upper position, as shown in FIG; 2, anotherannular channel 196 in the minor portion 178, located below the an nularchannel 190, bridges the passages 186 and 194. Thus, when the enginevalve 78 is in its lower position, the pilot valve 174 is also in itslower position and applies the valve operating pressure P Ap to thelower end of the engine valve actuator piston 98 by way of the passages182 and 1 On the other hand, when the engine valve 78 is in its upperposition, the pilot valve 174 is also in its upper position and appliesthe supply pressure P to the lower end of the engine valve actuatorpiston 98 by way of the passages 186 and 194.

Considering another aspect of the governing means 172, the upper land 86of the engine valve 78 is shorter in the axial direction than the lowerland 88 thereof. Consequently, as the engine valve 78 approaches eitherof its operating positions, the upper land 86 reaches its correspondingfully open position before the lower land 88 does, the correspondingV-shaped throttling grooves in the lower land 88 continuing to throttleflow under such conditions. To illustrate, as the engine valve 78approaches its upper position, the upper land 86 clears the passage 90before the lower land 88 clears the passage 94. Consequently, the upperend of the engine cylinder 40 is fully opened to the discharge pressureP by way of the pasbegins to build up to the supply pressure P sages 90and 92 while the flow of operating fluid at the supply pressure P intothe lower end of the engine cylinder by way of the passages 96 and 94 isstill being throttled by the V-shaped throttling grooves in the lowerend of the lower land, this being one of the throttling or governingpositions of the engine valve. A corresponding situation exists as theengine valve 78 approaches its lower position, except that the dischargeof operating fluid from the lower end of the engine cylinder 40 to P isthrottled after the upper end of the engine cylinder has been fullyopened to P this being the other throttling or governing position.

With the foregoing construction, the engine valve 78, its actuator 80and the pilot valve 174 cooperates to hold the engine valve in one orthe other of its aforementioned throttling positions if the load on theengine and pump plunger 32 is below a predetermined value for thecorresponding direction of movement of such plunger. In other words, theengine valve 78 stalls in .each of its throttling positions until theload on the plunger 32 reaches a predetermined value for thecorresponding direction of movement thereof. This action is fullyexplained in my aforementioned Patent No. 2,311,157 so that a completedescription herein is unnecessary.

Briefly, and considering only the case wherein the engine valve 78 hasreached its throttling or governing posi tion adjacent the end of itsupward movement, the upper end of the engine cylinder '40 is fully opento the discharge pressure P through the passages 90 and 92, while thelower end of the engine cylinder is only partially open to the supplypressure P through the passages 96 and 94. Under such conditions, thefull Pr-Pz is not applied to the plunger 32 in the upward direction sothat this plunger starts to move upwardly slowly. This results inmovement of the control channel 50 out of bridging relation with thecontrol passages 106 and 108. In view or" this, the engine valve 78cannot be caused to move upwardly all the way into its upper position bythe supply pressure P delivered to the lower end of the actuator piston98 by way of the control passage 108. Also, since the full supplypressure P is not delivered to the lower end of the engine cylinder 40through the passage 94, the full supply pressure P is not available inthe passage 188 to move the pilot valve 174 upwardly into its upperposition. Consequently, the engine valve 78 cannot complete its upwardmovement and remains stalled in its throttling or governing position.

Ultimately, the load on the engine and pump plunger 32 attains thepredetermined value mentioned, whereupon the pressure in the lower endof the engine cylinder 40 When this occurs, the full supply pressure Pis applied to the lower end of the pilot valve 174, causing this valveto shift upwardly into its upper position. Now, the full supply pressureP is applied to the lower end of the engine valve 78 by way of thepassages 186 and 194, whereupon the engine valve completes its upwardmovement into its upper operating position.

A similar action takes place if there is an insufiicient load on theengine and pump plunger 32 as the engine valve 78 approaches its loweroperating position.

Pump FIG. 3

The fluid operated pump illustrated in FIG. 3 of the drawings is similarin many respects to that of FIGS. 1 and 2. As a matter of convenience,therefore, the various components of the pump of FIG. 3 will beidentified by refernce numerals higher by two hundred than the referencenumerals used to designate corresponding components of the pump of FIGS.1 and 2.

Thus, the pump of FIG. 3 includes a bottom hole housing 210 having achamber 212 for an engine and pump unit 214 and a chamber 216 whichreceives therein the same engine valve unit 18 described previously.Connected to the bottom hole housing 210 are production and supplytubings 220 and 222 in communication with the 12 chambers 212 and 216,and also connected to the housing 210 is a return tubing 224.

The engine and pump unit 214 includes a housing 226 cngageable with anannular seat 228 and adapted to be unseated by fluid supplied through apassage 230. The engine and pump unit 214 includes a tubular plunger 232comprising an upper rod 234 reciprocable in a bore 236, an upper piston238 reciprocable in an upper cylinder 240, a lower rod 242 reciprocablein a bore 244, and a lower piston 246 reciprocable in a cylinder 248.The lower rod 242 is provided therein with external annular controlgrooves 250 and 252. The tubular plunger 232 carries a working valve 254in an axial passage 256 therethrough. The housings 226 and 210 arerespectively provided with inlets 258 and 260 respectively containingstanding valves 262 and 264. A port 266, a longitudinal groove 268 and aport 270 connect the inlet 258 to the upper end of the upper cylinder240.

The engine and pump unit 214 and the engine valve unit 18 areinterconnected by: a passage 290 corresponding to the passage butleading to the upper end of the lower cylinder 243; a passage 294corresponding to the passage 94 and leading to the lower end of theupper cylinder 240; a control passage 306 corresponding to the controlpassage 106, but leading to the bore 244; a control passage 308corresponding to the control passage 108, but leading to the bore 244,the control passages 306 and 308 being bridgeable by the control groove250; a control passage 300 corresponding to the control passage 100, butleading to the bore 244; a control passage 302 corresponding to thecontrol passage 102, but leading to the bore 244, the control passages300 and 302 being bridgeable by the control groove 252; a passage 388connected to the passage 294 and corresponding to the passage 188; and apassage 392 connected to the passage 302 and corresponding to thepassage 192.

With the pump of FIG. 3, the supply pressure P and the dischargepressure P are alternately applied to the lower end of the piston 238 byway of the passage 294 and the discharge pressure P and the supplypressure P are simultaneously alternately applied to the upper end ofthe piston 246 through the passage 290. Thus, the pump of FIG. 3 is adouble acting pump in which both of the pistons 238 and 246 serve as theengine piston, or, more accurately, the lower end of the piston 238 andthe upper end of the piston 246 serve as the engine piston. The pump ofFIG. 3 is also a differential pump in which both of the pistons 238 and246 cooperate to provide the differential pumping action. Thus, the pumpof FIG. 3 is basically similar to the pump of FIGS. 1 and 2, except thatin the FIG. 3 pump, the pumping means is, in effect, split into twoparts and the engine is inserted therebetween.

The engine valve unit 18 controls the engine and pump unit 214 of FIG. 3in the same manner that it controls the engine and pump unit 14 of FIGS.1 and 2. Consequently, a further description is not necessary.

Although exemplary embodiments of the invention have been disclosed forpurposes of illustration, it will be understood that various changes,modifications and substitutions may be incorporated in such embodimentswithout departing from the spirit of the invention as defined by theclaims which follow.

I claim:

1. In a fluid operated engine, the combination of: engine piston meansreciprocable by an engine-operating pressure differential applied tosaid engine piston means in opposite directions alternately; enginevalve means for applying said engine-operating pressure differential tosaid engine piston means, including a reciprocable engine valve; meansfor producing a valve-operating pressure differential which is mallerthan said engine-operating pressure differential; and means for applyingsaid valveoperating pressure differential to operate said engine valve.

2. In a fluid operated engine, the combination of: re-

ciprocable engine piston means movable in at least n direction by anengine-operating pressure differential applied to said engine pistonmeans; engine valve means for applying said' engine-operating pressuredifferential to said engine piston means, including a reciprocableengine valve; means for producing a valve-operating pressuredifferential which is smaller than said engine-operating pressuredifferential; and means for applying said valve-operating pressuredifferential to said engine valve in at least one direction.

3. in a fluid operated engine, the combination of: re ciprocable enginepistonmeans movable in at least one direction by an engine-operatingpressure dilferential applied to said engine piston means; engine valvemeans for applying said engine-operating pressure differential to saidengine piston means, including a reciprocable engine valve; means forproducing a valve-operating pressure differential which is smaller thansaid engine-operating pressure differential; and Ineansfor applying saidvalveoperating pressure differential to said engine valve in oppositedirections alternately.

4. In a fluid operated engine, the combination of: reciprocable enginepiston means movable in at least one direction by an engine-operatingpressure difierential of P P applied to said engine piston means, whereP is the supply pressure of an operating fluid and P is the dischargepressure thereof; engine valve means for applying P P to said enginepiston means, including a reciprocable engine valve; means for producinga valveoperating pressure differential of Ap which is independent of P-P and means for applying Ap to said engine valve in opposite directionsalternately.

5. In a fluid operated engine, the combination of: reciprocable enginepiston means movable in at least one direction by an engine-operatingpressure differential equal to the difference between supply anddischarge pressures P and P respectively, of an operating fluid; enginevalve means, including a reciprocable engine valve, for applying P P tosaid engine piston means; means for producing a valve operating pressurelying between the pres sures P and P and differing from one of them by avalve-operating pressure differential Ap which is independent of andsmaller than P P and means for applying Ap to said engine valve inopposite directions alternately to reciprocate said engine valve.

6. In a fluid operated engine, the combination of: reciprocable enginepiston means movable in at least one direction by an engine-operatingpressure differential of P -P applied to said engine piston means, whereP is the supply pressure of an operating fluid and P is the dischargepressure thereof; engine valve means, including a reciprocable enginevalve, for applying P P to said engine piston means; means for producinga valve operating pressure of P Ap where Ap is smaller than andindependent of P -P and means for applying to said engine valve inopposite directions alternately valve operating pressures of P and P--Ap.

7. In a fluid operated engine, the combinationof: reciprocable, enginepiston means movable in at least one direction by an engine-operatingpressure ditferential of P -P applied to said engine piston means, whereP is the supply pressure of an operating fluid and P is the dischargepressure thereof; engine valve means, including a reciprocable enginevalve, for applying P P to said engine piston means; means for producinga valve operating pressure of P +Ap where Ap is smaller than andindependent of P -P and means for applying to said engine valve inopposite directions alternately valve-opcrating pressures of P and P+Ap.

8. In a fluid operated engine, the combination of: reciprocable enginepiston means movable in at least one direction by an engine-operatingpressure differential of P P equal to the difference between supply anddischarge pressures P and P respectively, of an operating fluid; enginevalve means, including a reciprocable engine valve, for applying P P tosaid engine piston means; control means for producing a valve operatingpressure lying between the pressures P and P and differing from one ofthem by a valve-operating pressure dilferential Ap which is independentof and smaller than P P said control means including a source ofoperating fluid at said valve operating pressure, including a controlvalve communicating with said source and movable between open and closedpositions, including spring means biasing said control valve toward itsopen position, and including means for applying Ap to said control valvein a direction to bias it toward its closed position; and means forapplying Ap to said engine valve in opposite directions alternately toreciprocate said engine valve.

9. In a fluid operated engine, the combination of: reciprocable enginepiston means movable in at least one direction by an engine-operatingpressure differential of P P equal to the difference between supply anddischarge pressures P and P respectively, of an operating fluid; enginevalve means, including a reciprocable engine valve, for applying -P tosaid engine piston means, control means for producing a valve operatingpressure lying between the pressures P and P and differing from one ofthem by a valve-operating pressure dilferential Ap which is independentof and smaller than P --P means for applying Ap to said engine valve inopposite directions alternately to reciprocate said engine valve; andmeans incorporated in said control means for increasing Ap with anincrease in the viscosity of the operating fluid.

10. In a fluid operated engine, the combination of: reciprocable enginepiston means movable in at least one direction by an engine-operatingpressure dilferential of P -P equal to the diiference between the supplyand discharge pressures P and P respectively, of an operating fluid;engine valve means, including a reciprocable engine valve, for applyingP -P to said engine piston means; control means for producing a valveoperating pressure lying between the pressures P and P and dilferingfrom one of them by a valve-operating pressure differentialA p which isindependent of and smaller than P -P said control means including asource of operating fluid at said valve operating pressure, including acontrol valve communicating with said source and movable between openand closed positions, including spring means biasing said control valvetoward its open position, and including mean-s for applying Ap to saidcontrol valve in a direction to bias it toward its closed position;means for applying Ap to said engine valve in opposite directionsalternately to reciprocate said engine valve; and means incorporated insaid control means for increasing Ap with an increase in the viscosityof the operating fluid.

11. In a fluid operated engine, the combination of: reciprocable enginepiston means movable in at least one direction by an engine-operatingpressure diiferential of P -P equal to the difference between supply anddischarge pressures P and P respectively, of an operating fluid; enginevalve means, including a reciprocable engine valve, for applying P P tosaid engine piston means; control means for producing a valve operatingpressure lying between the pressures P and P and differing from one ofthem by a valve-operating pressure differential Ap which is independentof and smaller than P -P said control means including a source ofoperating fluid at said valve operating pressure, including a controlvalve communicating with said source and movable between open and closepositions, including spring means biasing said control valve toward itsopen position, and including means for applying Ap to said control valvein a direction to bias it toward its close position; means for applyingAp to said engine valve in opposite directions alternately toreciprocate said engine valve; and means for in creasing Ap with anincrease in the viscosity of the operating fluid, comprising means forapplying to said control valve, in direction biasing it toward its openposition, a

15 fluid pressure intermediate P and P varying as a function of theviscosity of the operating fluid.

12. In a fluid operated engine, the combination of: reciprocable enginepiston means movable in at least one direction by an engine-operatingpressure differential of P -P where P is the supply pressure and P isthe discharge pressure of an operating fluid; engine valve means,including a reciprocable engine valve movable from one operatingposition to another, open operating position through an intermediate,governing position, for applying P P to said engine piston means atleast when said engine valve is in said other, open operation; means forproducing a valve operating pressure lying between the pressures P and Pand dilfering from one of them by a valve-operating pressuredifferential Ap which is independent of and smaller than P -P means forapplying A to said engine valve in opposite directions alternatively toreciprocate said engine valve; and auxiliary valve means for holdingsaid engine valve in said governing position when no load is on saidengine piston means.

13. In a fluid operated engine, the combination of: reciprocable enginepiston means movable in at least one direction by an engine-operatingpressure dilferential of P P where P is the supply pressure and P is thedischarge pressure of an operating fluid; engine valve means,

Ap to said engine valve in opposite directions alternately toreciprocate said engine valve; and auxiliary valve means controlled bysaid engine valve means and controlling the application of Ap to saidengine valve for holding said engine valve in said governing positionwith no load on said engine piston means.

References Cited in the file of this patent UNITED STATES PATENTS2,223,792 Muir Dec. 3, 1940 2,304,131 Vickers Dec. 8, 1942 2,311,157Coberly Feb. 16, 1943 2,566,295 Alward Sept. 4, 1951 2,746,431 TebbettsMay 22, 1956 2,942,552 Wayt June 28, 1960 2,950,685 Salentine Aug. 30,1960 UNITED STATES PATH" OFFICE CERTIFICATE OF CORRECTION Patent No.3,082 749 March 26, 1963 Clarence J. Coberly It is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as corrected below Column 9, line17, for "pressured" read pressure line 32, for "passage" read passagescolumn 11, line 14, for "cooperates" read cooperate line 67, for"refernce" read reference column 13 lines 58 and 59, after "reciprocablestrike out the comma; column 14, line 34, strike out "the", secondoccurrence; column 15, line 1 after "P insert and line 12, for"operation" read operating position line 17 for "alternatively" readalternately column 16 llne 7, for "pressure" read pressures Signed andsealed this 29th day of October 1963.

(SEAL) Attest:

EDWIN L. REYNOLDS ERNEST W. SWIDER Attesting Officer Ac tingCommissioner of Patents

1. IN A FLUID OPERATED ENGINE, THE COMBINATION OF: ENGINE PISTON MEANSRECIPROCABLE BY AN ENGINE-OPERATING PRESSURE DIFFERENTIAL APPLIED TOSAID ENGINE PISTON MEANS IN OPPOSITE DIRECTIONS ALTERNATELY; ENGINEVALVE MEANS FOR APPLYING SAID ENGINE-OPERATING PRESSURE DIFFERENTIAL TOSAID ENGINE PISTON MEANS, INCLUDING A RECIPROCABLE ENGINE VALVE; MEANSFOR PRODUCING A VALVE-OPERATING PRESSURE